88 lines
3.1 KiB
Python
88 lines
3.1 KiB
Python
"""Precompute CIE2000 perceptual colour distance matrices.
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The matrix of delta-E values is computed for all pairs of 24-bit RGB values,
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and Apple II target palette values. This is written out as a file that is
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mmapped at runtime for efficient access. For a 16-colour target palette this
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file is 256MB; for a 256-colour (NTSC) target palette it is 4GB.
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"""
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import argparse
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import os
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import image
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import palette as palette_py
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import colour.difference
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import numpy as np
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RGB_LEVELS = 256
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# Largest possible value of delta_E_CIE2000 between two RGB values
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DELTA_E_MAX = 120 # TODO: fine-tune
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def rgb_to_lab(rgb: np.ndarray):
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srgb = np.clip(
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image.linear_to_srgb_array(rgb.astype(np.float32) / 255), 0.0,
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1.0)
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xyz = colour.sRGB_to_XYZ(srgb)
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return colour.XYZ_to_Lab(xyz)
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def all_lab_colours():
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all_rgb = np.array(tuple(np.ndindex(RGB_LEVELS, RGB_LEVELS, RGB_LEVELS)),
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dtype=np.uint8)
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return rgb_to_lab(all_rgb)
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def nearest_colours(palette, all_lab, diffs):
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palette_size = len(palette.RGB)
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palette_labs = np.empty((palette_size, 3), dtype=np.float)
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for i, palette_rgb in palette.RGB.items():
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palette_labs[i, :] = rgb_to_lab(palette_rgb)
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print("Computing all 24-bit palette diffs:")
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for i in range(palette_size):
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print(" %d/%d" % (i, palette_size))
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# Compute all palette diffs for a block of 65536 successive RGB
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# source values at once, which bounds the memory use while also writing
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# contiguously to the mmapped array.
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diffs[i * (1 << 16):(i + 1) * (1 << 16), :] = (
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colour.difference.delta_E_CIE2000(
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all_lab[i * (1 << 16):(i + 1) * (
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1 << 16)].reshape((1 << 16, 1, 3)),
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palette_labs.reshape((1, palette_size, 3))) / DELTA_E_MAX *
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255).astype(np.uint8)
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def main():
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parser = argparse.ArgumentParser()
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parser.add_argument('--palette', type=str, choices=list(
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palette_py.PALETTES.keys()),
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default=palette_py.DEFAULT_PALETTE,
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help="Palette for which to compute distance matrix.")
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parser.add_argument('--all', type=bool, default=False,
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help="Whether to compute distances for all palettes")
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args = parser.parse_args()
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if args.all:
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palette_names = list(palette_py.PALETTES.keys())
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else:
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palette_names = [args.palette]
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print("Precomputing matrix of all 24-bit LAB colours")
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all_lab = all_lab_colours()
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for palette_name in palette_names:
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print("Creating distance file for palette %s" % palette_name)
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palette = palette_py.PALETTES[palette_name](load_distances=False)
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try:
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os.mkdir(os.path.dirname(palette.DISTANCES_PATH))
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except FileExistsError:
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pass
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out = np.memmap(filename=palette.DISTANCES_PATH, mode="w+",
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dtype=np.uint8, shape=(RGB_LEVELS ** 3,
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len(palette.RGB)))
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nearest_colours(palette, all_lab, out)
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if __name__ == "__main__":
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main()
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